One example of a self-piercing rivet setting machine is described in Japanese Patent Laid-Open No. 8-505087. FIG. 1 therein shows one example of a self-piercing rivet. The self-piercing rivet comprises a flange-shaped head and a leg extending downward from the head. When the self-piercing rivet is driven into workpieces, such as two car body panels, by using a punch and a die, the leg is deformed to expand the edge of the leg while piercing (boring) the panels. In this manner, the both panels are connected with each other through the expandedly deformed leg and the head. The self-piercing rivet is suitable for assembling an aluminum body to which welding is not applicable. Since aluminum bodies are increasingly employed to facilitate weight reduction in automobile bodies, the demand for the self-piercing rivet would increase in the future.
While not shown in the aforementioned publication, Japanese Patent Laid-Open No. 11-90575 shows one example of a self-piercing rivet setting machine in FIG. 2 thereof. As shown in that figure, the self-piercing rivet setting machine comprises a C-shaped frame including an upper horizontal arm, a vertical arm, and a lower horizontal arm. The self-piercing rivet setting machine further includes a punch provided at one end of the C-shaped frame, a die provided at the other end of the C-shaped frame, and a punch driving means, such as a motor and a spindle, for pressing the punch against the die to press a self-piercing rivet supported by the punch against the die. A plurality of members are placed between the punch and the die to be connected with each other by driving the self-piercing rivet into the members while piercing the members by the self-piercing rivet. A conventional rivet setting machine typically includes a feeding device and receiver means for automatically feeding rivets to a punch. These components can be attached to a self-piercing rivet setting machine. Actually, there is a self-piercing rivet setting machine equipped with these components. In that machine, the punch is attached to the edge of a receiver unit for receiving the self-piercing rivet fed from the feeding device to hold the self-piercing rivet therein The punch is moved toward the die by the punch driving means provided on one end of the C-shaped frame. Then, a plurality of members are placed between the punch and the die to be connected with each other by driving the self-piercing rivet in the members while piercing the members by the self-piercing rivet. Such conventional self-piercing rivet setting machines can advantageously achieve and maintain high sealing performance to the interior of an automobile because the leg of the self-piercing rivet can connect the workpieces each other without penetrating therethrough.
As described above, the self-piercing rivet setting machine essentially comprises the C-shaped frame including the upper horizontal arm, the vertical arm and the lower horizontal arm. In order to resist high riveting load or force, the C-shaped frame is typically formed in an integral structure. Thus, upon no-operation of the setting machine, there is a certain but not so great distance between the punch disposed at one end of the C-shaped frame (the end of the upper horizontal arm) and the die disposed at the other end of the C-shaped frame (the end of the lower horizontal arm) depending upon the size of the C-shaped frame. When the workpieces are simple flat plates, they are relatively easy to locate them between the punch and the die. However, when the workpiece partially includes a standing wall extending therefrom at a right angle, there is sometime the case that the workpiece cannot be positioned between the punch and the die. In that case, it is require to replace the C-shaped frame with a lager C-shaped frame so as to increase the distance between the punch and the die. However, the overall size of the setting machine is increased due to the larger C-shaped frame having rigidity for resisting the high riveting load. Further, the driving means has a specific stroke for moving the punch of the setting machine. Thus, it is impractically necessary to replace with larger driving means designed for the larger C-shaped frame. As a result, a portion of the workpieces might not be connected, due to the shape of the workpieces. Further, the punch driving means includes a spindle fixedly connected with the receiver unit to which the punch was attached. This also constrains a settable region of workpieces to be connected.
It is therefore an object of the present invention to provide a self-piercing rivet setting machine capable of handling even a particular workpiece which has a standing wall requiring an widened distance between a punch and a die, without any need for providing a larger C-shaped frame.